Silica-alumina-nickel dehydrogenation catalyst



Jan. 31, 11950 B. B. CORSON ET AL 2,495,700

SILICA-ALWINA-NICKEL DEHYDROGENATION CATALYST Original Filed Oct. 9, 1944 @IGf/T PER CEN T CONVERSION TO STfRE/VE PER P085 o 1 .2 :s 4 5 s a rzms IN HOURS 5 1 Z NICKEL o/y E vim 2 5 2 2 k 0 "3 I s /WEV. 4/ 0 25% $0; Q 23 8 2o %H k E 2 g 10 2 u q l \IVENTORS. TIME HOURS 551v BENNETT CoesoN, F

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ATTORNEY hot vapor atented Jan. 31, 1950 SILICA-ALUMINA-NICKEL DEHYDROGENA- TION CATALYST 1 Ben Bennett Corson an d George Arthur Webb, ttsburgh, Pa., assignors to Koppel-s Company,

Inc., Pittsburgh, Pa., a corporation of Delaware Original application October 9,

- 3 Claims.

The present invention relates to the dehydrogenation of hydrocarbons and to catalysts therefor. More particularly the invention relates to the dehydrogenation of aliphatic hydrocarbons or of aliphatic chains when attached to aromatic hydrocarbons.

It is known to the art that hydrocarbons can be dehydrogenated pyrolytically and catalytically and that the success of a given process depends upon the efiiciency by which the dehydrogenation reaction occurs in preference to other side reactions or decomposition reactions. Pyrolytic processes in general require higher operating temperatures to obtain practical dehydrogenating rates, and at these higher temperatures the tendency toward side reactions is increased, resulting in poor operating efliciency. In the so-called processes, that are modifications oi the pyrolytic processes, the hydrocarbon to be dehydrogenated is added directly to a highly superheated vapor such as steam and alter an extremely short contact time the mixed vapors are quenched with liquid water, or the like, and are rapidly reduced below temperatures for side cracking reactions.

Catalysts in general provide contact surfaces at which the dehydrogenation reaction can proceed at lower than pyrolytic process temperatures and usually with diminished decomposition or side cracking reactions. The hot vapor processes can be used with catalysts and the economies inherent to operating at a lower temperature and with the reduced pressure effects of a diluent are thus obtained. In this case, however, it is important to choose catalysts which are not afiected deleteriously by water and which give practical dehydrogenation rates.

Many dehydrogenation catalysts have been proposed, among the most active being the oxides of metals that are diflicultly reducible under the conditions of working such as silica, alumina, magnesia, lime, ceria, chromia, and the like, either alone or in admixture with each other. A particularly good dehydrogenation catalyst results from the admixture of chromia and alumina. It has also been proposed to improve the catalytic activity of these difiicultly reducible oxides with metals such as copper, cobalt, and iron. Nickel oxide which can be easily reduced with hydrogen to the metal, has, however, been generally avoided because under the conditions previnus v em loyed there have resulted uneconomical decomposition side reactions and carbon formation.

It has now been discovered that under proper operating conditions nickel can be employed to 1944, Serial No.

Divided and this application March Serial No. 653,405

improve dimcultly reducible oxide catalysts, and that such nickel impregnated catalysts have improved catalytic activity particularly in the presence of large volumes of water and especially for the dehydrogenation of the aliphatic side chains of alkyl aryl hydrocarbo A primary object of the present invention is to provide improved dehydrogenation catalysts, especially of the type comprising difiicultly reducible metal oxides.

A further object of the present invention is to provide a catalytic process for dehydrogenating hydrocarbons in the presence of diluent water vapor.

Another object of invention is to provide an improved process of dehydrogenating hydrocarbons such as aliphatic hydrocarbons and the allphatic chains attached to aromatic hydrocarbons.

Another object of invention is to provide a. process for the dehydrogenation of alkyl aryl hydrocarbons to produce aikenyl aryl hydrocarbons.

Still another object of invention is to provide a process for the dehydrogenation of paraflins to olefins.

The invention has for further objects such other improvements and such other operative advantages or results as may be found to obtain in the processes hereinafter described or claimed.

Accordingto the present invention it has been found that dehydrogenation catalysts and especially those catalysts comprising one or more of the oxides of metals that are difilcultly reducible under the conditions of working, such as silica, alumina, magnesia, lime, ceria, chromia, and the like, when treated with a small amount of nickel to impregnate the catalyst, give improved results in dehydrogenation reactions, and especially in dehydrogenation reactions where relatively large quantities of water vapor are employed to advantage. The quantity of nickel employed must be less than that producing the known and undesirable cracking reactions and is usually less than 3 percent and preferably about one percent of the total catalyst weight.

To increase the length of the operating cycle with catalysts such as those comprising the dimcultly reducible metal oxides, the feed stock is often diluted with water vapor. By the use of such a diluent, the on stream" life of the catalyst has been increased, probably largely due to the decreased deposition of carbon on the catalyst. In the past, this benefit has been substantially or at least partially offset by the fact that the water vapor exerted an initial poisoning efiect on the catalysts, resulting in a proaeoavoo longed induction period before the catalysts functioned with maximum effectiveness.

The poisoning effect of water on a difiicultly reducible oxide catalyst varies with composition of the catalyst, the amount of water used, and the temperature. Small amounts of water do not seriously decrease the initial conversions, or with small amounts of water the length of the inactive period is so short as to be of no practical significance. As the water ratio is increased, the time required for the catalytic activity to reach a maximum is extended. For example, when operating with an activated alumina catalyst at 650 C. and a 2.521 mol ratio of water to the tobe-dehydrogenated ethylbenzene, three hours time were required to reach the peak activity. At the same temperature but with a 10:1 mol ratio of water to ethylbenzene, peak activity was not reached until the unit had been on stream for ten hours. However, the higher diluent ratio gave a higher conversion. Further, with the hot vapor processes high diluent ratios are necessary in order to provide sufficient heat for dehydrogenating the hydrocarbon feed.

The induction period for the difilcultly reducible oxide catalysts varies with the composition. The following catalyst materials when tested under identical operating conditions for the dehydrogenation of ethylbenzene to styrene had induction periods as follows: activated alumina. 10 hours, magnesia, 15 hours, and dolomite 25 hours.

By the impregnation of a catalyst comprising one or more difllcultly reducible metal oxides with less than 3 percent and preferably about one percent of nickel the long induction period or poisoning effect due to the use of water vapor, is substantially and often almost completely eliminated. The nickel-impregnated catalyst functions with maximum effectiveness at times in a matter of minutes after going "on stream, whereas the unimpregnated catalyst usually takes several hours before its peak efficiency is attained. Surprisingly, the increased hydrocarbon conversion obtainable with the nickel impregnated catalyst is not offset by any appreciable increase in carbon deposition on the catalyst, therefore the on stream" life of a nickel-impregnated catalyst is substantially the same as for an unimpregnated catalyst. It is a very important advantage that the gain in conversion does not carry the penalty of a decreased catalyst life.

The important reduction in the induction period and the elimination of the poisoning effect of water by impregnating diflicultly reducible metal oxide catalysts with but one percent by weight of nickel are clearly illustrated in the attached drawing wherein Figure l is a diagram showing the weight percent conversion to styrene per pass versus time in hours for a typical conversion of ethylbenzene to styrene over an activated alumina catalyst, with and without nickel impregnation. The water to ethylbenzene molar ratio was 5:1. The impregnated catalyst operated at high efficiency after about a half hour whereas it took about four hours for the unimpregnated catalyst to attain comparable efficiency.

Figure 2 is a diagram similar to Figure 1, where a mixed alumina-silica catalyst was employed, the water to ethylbenzene molar ratio being :1. In this conversion the unimpregnated catalyst never attained the conversion efficiency of the nickel-impregnated catalyst. The increased styrene production with nickel impregnation is represented by the area between the two curves.

These typical tests will be more fully described in the hereinafter given specific examples.

Ordinarily, because of the aforementioned increased conversion and catalyst life obtainable, it is preferred to operate a nickel-impregnated, diillcultly reducible, metal-oxide, dehydrogenation catalyst in the presence of water vapor, especially for conversions in a. temperature range of from 500 C. to 750 C. This is especially true for the conversion of ethylbenzene or other alkylated aromatic hydrocarbons to styrene or an analog thereof or for the conversion of a paraffin having at least three carbon atoms in the molecule to an olefin, such as the conversion of isobutane to isobutylene.

The catalyst can be prepared by impregnating a dehydrogenation catalyst, for example, a chillcultly reducible metal oxide or mixtures of metal oxides with a nickel salt, for example, nickel nitrate. A sufficient amount of nickel salt solution, for example, is used to provide about one percent deposit by weight of the element nickel on the metal oxide carrier. Upon heating the metal oxide impregnated with the nickel salt in an oxidizing atmosphere the nickel salt is decomposed to form nickel oxide. The metal oxide impregnated with nickel oxide can be used directly in a dehydrogenation chamber and the hydrocarbon passed thereover for treatment. The dehydrogenation of the hydrocarbon will produce suiilcient hydrogen to reduce the nickel oxide to metallic nickel, or what is of prime importance, will form a catalyst which is just as effective as a catalyst that has been prepared by the alternative method of first reducing with hydrogen the nickel oxide impregnated metallic oxide.

The nickel can be added during any stage in the preparation of a catalyst. With a porous catalyst the nickel will penetrate the catalyst, while with a denser catalyst the penetration will not be as great. In the following specific examples about one percent nickel has been used with a number of different catalysts in order to compare the results obtainable thereby. Some types of catalysts will operate efllciently with considerably less than a one percent nickel content, whereas others give better results with a little over one percent nickel. In any case, the active surface will probably hold more or less nickel depending largely on the physical condition of the particular catalyst used.

In using the. catalyst in the dehydrogenation process, the catalyst is preferably supported in tubes, such as glass, porcelain or metal tubes that may be heated in a furnace to develop the desired temperature in the catalyst bed. The hydrocarbon feed stock is preferably preheated and vaporized at a temperature of about 300 C. to 400 C. before passing it over the heated catalyst. In a hot vapor process the feed stock is vaporized and preheated to about 400 C. before it is mixed with the superheated steam to produce the preferred temperature for contact with the catalyst in an insulated tube.

When the dehydrogenation is carried out at high temperatures at from 500 C. to 750 C. it is generally desirable to quench and quickly condense the products of reaction to avoid any secondary reactions taking place. The preferred product of reaction can be obtained by distilling the condensate. The unconverted feed stock can then be recycled to the dehydrogenation zone.

When the activity of these catalysts has diminished, due to the formation of a carbonaceous deposit upon the surface thereof, the hydrocarhon feed is shut oil and the system is purged with an inert gas such as steam, nitrogen, CO2, etc., to remove the volatile combustion matter. The deposited carbonaceous material is then burnt on and the catalyst surface reactivated by simply condition without loss of catalytic efliciency and 1.,

the resulting nickel oxide can be again reduced to metallic nickel with hydrogen as previously described. w

The following examples illustrate some of the methods for preparing the improved catalyst of the invention and some of the dehydrogenation results obtained by use of the said catalysts. In the following examples the term conversion per pass means the percent by weight of the total hydrocarbon feed stock converted to product.

The term ultimate yield" is the percent by weight oi reacted hydrocarbon feed stock converted to product.

Example No. 1

A dehydrogenation catalyst was prepared by impregnating a pilled commercial activated alumina with a solution of nickel nitrate. The impregnated alumina after partial dehydration was heated at about 450 C. for two hours 3.3

in a current of air thus leaving thereon mo in such amount that the nickel represented about one percent of the dry weight of the alumina. Water and ethylbenzene in a molar ratio of 5:1 were vaporized at 350' through a copper-lined tube filled with the nickel impregnated catalyst. The catalyst temperature was 650 C. with one second contact time. The liquid product from an 8-hour run analyzed 53.5

percent styrene.

The activated alumina without nickel impregnation when tested under the same conditions gave a liquid product for an 8-hour run that analyzed only 43.7 percent styrene.

Figure 1 in the drawing was plotted from the results obtained in this test and illustrates the long induction period of about 4.5 hours required before the unimpregnated alumina attained the emciency of the nickel impregnated alumina. The increased sented by subtracting the small area between the two curves from the large area.

Example 2 A dehydrogenation catalyst was prepared by 6' mixing aluminum chloride with silica gel in the correct proportions to give a 75 %-25% aluminasilica mixture. The alumina was precipitated The control of i0 C. and then passed production of styrene is repre- 6 v with ammonia and the mixture was washed free of chlorides, dried at 100 C., and pilled into M," x M," cylinders. A portion 01' this pilled catalyst was impregnated with suflicient nickel nitrate to have about one percent nickel on the total weight oi alumina silica. catalyst was then dried in an oven and finally heated at 600 C. for several hours.

Water and ethylbenzene in a mo] ratio of 10:1 were vaporized at 350 C. and then passed through a copper-lined tube filled with the nickel impregnated alumina-silica catalyst. The catalyst temperature was 650 C. with 0.25 second contact time. The liquid product from 8- hour run was light brown and analyzed 46 pe i ent styrene. The carbon deposit on the catalyst amounted to 1.77 percent-of the ethylbenzene charged.

The above alumina-silica nickel impregnation when tested under the same runs, with nickel 42% styrene, without nickel 21% styrene. For the second two hour period, with nickel 50% styrene, without nickel 37% styrene. Comparable carbon deposits indicate comparable catalyst life before regeneration.

Example 3 The commercial activated alumina catalyst and nickel impregnated alumina catalyst described in Example 1 were compared for dehydrogenating ethyl naphthalene to vinyl naphthalene. Water and ethyl naphthalene in a mo] ratio of 10.71 were vaporized at 300 C. and

The catalyst temperature was 650 C. with a one-second contact time. The liquid product from a 30-hour run analyzed 41% vinyl naphthalene. The alumina catalyst without nickel impregnation when tested under the same conditions gave a liquid product from a 30-hour run that analyzed 38% vinyl naphthalene.

Example 4 Comparison tests were run with catalysts impregnated with about one percent nickel and unimpregnated catalysts for the dehydrogenation of ethylbenzene to styrene. The test conditions for 4-hour runs and the results obtained have been summarised in the following table:

Average Ethyl Ultimate Temperature Contact Styrene catalyst of Catalyst Time zf Conversion gl g Ratio per Pass y C. Seconds Percent Percent Activated alumina 650 l 5 1 32 72 1% Nickel on activ ted alumina 1 5 l 52 75% alumina-25% silica. 650 0.25 10:1 31 62 1% Ni on 75% alumina 25% silic 650 0. 25 10:1 46 alumina-15% chromia 650 1 5:1 '41 69 1% Ni on 85% alumina-l5% chromia 650 l 5 1 49 68 granular particle, and

In terms of styrene production over this 4- hour cycle, the higher conversions per pass due to impregnation with 1% nickel represented increases of 62.5% for the activated alumina,

48.4% for the alumina-silica and 19.5% for the alumina-chromia catalysts.

Example 5 First llonr (ntnlyst Composition Conversion lm Pass Per Cent 85%A)O|'15%Cffl0l l3 1% Ni on 85% Ai1O;-l5% C110; 24 Activated alumina 7 1% Ni on activated alumina 14 Example 6 A catalyst was prepared from magnesite by grinding and screening to give an 8-14 mesh calcining in a current of air at 800 C. for six hours. These granules were then mixed with sufficient nickel nitrate to give about 1% nickel. The mixture was evaporated on a water bath, dried at 100-105 C., and heated at 600-650 C. to decompose to nickel oxide. This catalyst was used to dehydrogenate ethylbenzene to styrene at 650 C., 0.5 second contact time, and with a diluent ratio of 10 mols of steam to one moi of ethylbenzene. For a l60-hour period the overall average styrene production was per pass with an average ultimate yield of about 89%. Over this long operating period the carbon deposition amounted to 0.3% of the ethylbenzene feed.

Without the nickel impregnation, a contact time of 0.8 second was required for an average conversion of 36% styrene. Thus the nickel impregnation increased the throughput over the catalyst at the given temperature by 60%.

The advantages of the small amount of added nickel are not restricted to operations in the presence of water for reactions involving the dehydrogenation of the aliphatic side chain of aromatic compounds. In these reactions, the addition of nickel to diiiicultly reducible metal oxide catalysts increases the catalytic activity as shown by improved conversions at a. given temperature without any loss in efiiciency. This is illustrated in the following examples:

Example 7 The nickel impregnated catalyst described in Example No. lwas employed for ethylbenzene conversion to styrene without a water diluent. The catalyst was charged into a pyrex glass tube and placed in a reaction furnace. Ethylbenzene was preheated to 300 C. and passed at a rate of 40 cc. per hour over 20 cc. of this catalyst at a temperature of 650 C. The pale yellow liquid condensate had a styrene concentration. The liquid product represented 94.6% of the ethylbenzene charge. The ultimate yield, allowing for the unreacted ethylbenzene was 70%.

The pilled commercial activated alumina without nickel impregnation when used as a catalyst the nickel nitrate under the same conditions gave a liquid condensate containing 35% styrene, and an ultimate yield of 71%.

Under the same conditions except that the treating temperature was 600 C. rather than 650 C., with the nickel-impregnated alumina catalyst the condensate had a 28% styrene concentration and represented 97.5% of the ethylbenzene charge. With alumina alone the condensate contained only 5% styrene. The nickel impregnated catalyst retained a major portion of its activity at 600 C., whereas the activity of the alumina alone had almost disappeared. Nickel impregnation of a catalyst permits conversion at a lower temperature or gives higher yields than an unimpregnated catalyst at a given optimum temperature.

Example 8 The catalysts of Example No. 2 were used to dehydrogenate ethylbenzene to styrene, without use of water vapor. Ethylbenzene preheated to 300 C. was passed over the nickel-impregnated catalyst at a liquid hourly space velocity of 4 and a temperature of 650 C. The liquid condensate collected represented of the ethylbenzene charge and contained 28% styrene.

The pilled catalyst comprising 75% A: and 25% SiOz without nickel impregnation under the same conditions gave a liquid condensate containing only 12% styrene.

Example 9 Comparison tests were run with commercial activated alumina and alumina impregnated with about one percent nickel for the dehydrogenation of isopropyl benzene to methyl styrene. The runs were made at 650 C. and one second contact time, the weight percent of methyl styrene per pass was 34% with the activated alumina and 45% with the nickel-impregnated activated alumina.

The actual yields obtained with these catalysts, are a function of the contact time. For example. with a one percent nickel on alumina catalyst the conversion per pass, over a 12-hour operating cycle at 650 C. and a 5:1 moi ratio of water as diluent, drops from about 50% to 30% as the contact time is decreased from 1.0 to 0.1 second. However, over this decrease in the contact times, the ultimate yield can be improved by about 10%. Obviously in large scale commercial operations with these catalysts, the contact time would be chosen for optimum conversion. This contact time would probably be in the range of 0.4 to 0.5

second.

The hereinabove described specific examples illustrate some of the dehydrogenation reactions for aliphatic hydrocarbons and aliphatic chains of aromatic hydrocarbons that are importantly improved by impregnating typical dehydrogenation catalysts with less than 3% nickel. In addition to the difiicultly reducible oxides, nickel impregnation can be used to promote other dehydrogenation catalysts, as for example, chromiumphosphate, calcium phosphate, zinc sulphate, barium-aluminate, calcium-aluminate, magnesium-phosphate, and also the heavy metallates of these metals such as vanadates, molybdates, tungstates, and chromates. Dehydrogenation catalysts impregnated with less than 3% nickel can also be employed to advantage in other typical dehydrogenation reactions, for example, for the dehydrogenation of naphthenes, such as cyclohexane and methyl cyclohexane. Where diluent water is mixed with the feed stock to improve catalyst life, the nickel impregnation reduces the induction period for dehydrogenation catalysts and reactions.

It is known to reduce the cracking activity of nickel in reactions by sulphiding a nickel containing catalyst with hydrogen sulphide, or the like, before use. The cracking activity is reduced where more than about nickel is used. However, in the above described dehydrogenation reactions where about one percent nickel was employed, the results obtained with a sulphided nickel catalyst were poorer than with nickel alone, both with and without water dilution.

This application constitutes a division of our application Serial No. 557,914 filed October 9, 1944 for Dehydrogenation process and catalysts."

The invention as hereinabove set forth is embodied in particular form and manner but may be variously embodied within the scope of the claims hereinafter made.

We cla:

1. A catalyst for eficient dehydrogenation of hydrocarbons consisting essentially of a major portion of alumina and a minor portion of silica activated with about 1% and less than.3% of the oxide mixture of nickel capable of maintaining the dehydrogenation activity of the catalyst at temperatures of 650 C. in the presence of steam.

2. A catalyst for emcient dehydrogenation of hydrocarbons consisting essentially of a mixture of 75% A120: and 25% S102 activated with about 1 by weight of metallic nickel based on the oxide REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,203,826 Komarewsky June 11, 1940 2,331,338 Michael et al Oct. 12, 1943 2,340,935 Connolly Feb. 8, 1944 2,342,856 Hall Feb. 29, 1944 2,365,029 Voorhies Dec. 12, 1944 2,389,500 Goshorn Nov. 20, 1945 2,394,796 Marisic Feb. 12, 1946 2,408,131 Voorhies Sept. 24, 1946 OTHER REFERENCES Zelinsky and Komarewsky. "Ber. Deut. Chem, Jahrg. 57, (1924) pages 667-669. 

1. A CATALYST FOR EFFICIENT DEHYDROGENATION OF HYDROCARBONS CONSISTING ESSENTIALLY OF A MAJOR PORTION OF ALUMINA AND A MINOR PORTION OF SILICA ACTIVATED WITH ABOUT 1% AND LESS THAN 3% OF THE OXIDE MIXTURE OF NICKEL CAPABLE OF MAINTAINING THE DEHYDROGENATION ACTIVITY OF THE CATALYST AT TEMPERATURES OF 650*C. IN THE PRESNECE OF STEAM. 